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Trawling for trash in Sydney Harbour to understand plastic’s impacts

Sydney Harbour is hosting Danish tall ship Yukon from today, but not for the usual historical re-enactments. Instead, this trip is about the not-so-fantastic impact of modern Australian society and its discarded plastics on the marine ecosystem.

Professor Richard Banati and a team from the Australian Nuclear Science and Technology Organisation are trawling the harbour for plastic debris, as part of an odyssey from Hobart to Sydney to further ANSTO research on how plastics break down in the marine environment and the impact they have on maritime species and the food chain.

The team’s work is disproving the old adage that “the solution to pollution is dilution”. Working with the tracer principle in collaboration with Dr Jennifer Laver from Monash University, Dr Banati showed that only not does the average shearwater’s stomach contain 10 per cent plastic, elements from the plastic have found their way into the feathers of the birds, raising the possibility that potentially toxic contaminants such as cadmium transfer into the body after ingestion and remain there after excretion.

His preliminary findings, released in April this year, are that the complex degradation process of plastics floating in the ocean makes them potentially more hazardous than previously thought.

During the process of degradation, plastics break down into smaller and smaller pieces, this increases the surface area dramatically, and increases the rate of release of toxins, including cadmium and mercury, into the environment, including its wildlife.

The trawling operation is being undertaken to increase the size of Dr Banati’s sample, which will then be analysed by a range of methods in order to better understand the impacts different types of plastics have on the marine ecosystem and food chain.

Image credit: Paul K Robbins / Monde photo

Image credit: Paul K Robbins / Monde photo

Australia’s plastic dump

Also this month, a new report by the CSIRO shows that most of the plastic found along Australia’s beaches has its origins right here at home.

CSIRO scientist Denise Hardesty said her team surveyed sites approximately every 100 kilometre along the Australian coastline, and found that about 75 per cent of the rubbish along the coast was plastic, most of it from Australian sources rather than washing in on the tides from the high seas. The debris concentrated near cities, and ranges in density from a few thousand pieces of plastic a square kilometre to more than 40,000 pieces a square kilometre.

“Approximately one third of marine turtles around the world have likely ingested debris, and this has increased since plastic production began in the 1950s,” Dr Hardesty says. “We also estimate that between 5000 and 15,000 turtles have been killed in the Gulf of Carpentaria after becoming ensnared by derelict fishing nets mostly originating from overseas.”

She said the Tasman Sea south of Australia was a global hotspot for seabird impacts.

“We found that 43 per cent of seabirds have plastic in their gut. Globally, nearly half of all seabird species are likely to ingest debris, eating everything from balloons to glow sticks, industrial plastic pellets, rubber, foam and string.”

“By garnering the information needed to identify sources and hotspots of debris, we can better develop effective solutions to tackle marine debris,” Dr Hardesty said.

UNSW researchers map plastic origins

UNSW researchers have also been examining the detritus that floats in the world’s oceans, developing a new model that could help determine who is to blame for the rubbish that makes up The Great Pacific Garbage Patch between Hawaii and California, believed to be one of at least five such patches of polluting plastics located in the centre of large, circular ocean currents called gyres that suck in and trap floating debris.

“In some cases, you can have a country far away from a garbage patch that’s unexpectedly contributing directly to the patch,” Gary Froyland, a mathematician at UNSW said. For example, the ocean debris from Madagascar and Mozambique would most likely flow into the south Atlantic, even though the two countries’ coastlines border the Indian Ocean.

The new model could also help determine how quickly garbage leaks from one patch into another, according to Erik van Sebille, an oceanographer who collaborated with Froyland and mathematician Robyn Stuart on a research paper published in Chaos, an American scientific journal.

“We can use the new model to explore, for example, how quickly trash from Australia ends up in the north Pacific,” van Sebille said.

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